In a wireless communication system, the RF power amplifier (PA) is one of the major power-consuming devices. Therefore, improving the efficiency of power amplifier can effectively reduce system power consumption.
The power efficiency of power amplifier is negatively correlated to its linearity. When a system is operating in its non-linear region of the power amplifier, it will cause distortion to in-band signal and out-band spectral spreading, therefore further deteriorating the performance of the overall system. Further, modulation techniques (such as Orthogonal Frequency Division Multiplexing (OFDM)) adopted by communication systems with high spectral efficiency are even more sensitive to non-linearity of the power amplifier.
Effective ways to improve linearity of the power amplifier include a feed-forward (Feed-Forward) technology, negative feedback technology and predistortion technology. Digital based predistortion (or digital predistortion) technology has the advantage of high stability, low cost, and suitable for wideband signals.
Digital predistortion technology may be implemented using a polynomial method. The digital predistortion technology based on common digital polynomial has the disadvantage of slow convergence and low numerical stability, because of the high correlation among columns of the matrix used for deriving pre-distortion model parameters. Therefore, it is desirable to design a circuit and a method to increase convergence speed to derive the predistortion model parameters.